Stroke survivors may have 80% higher risk of dementia

People with stroke have an approximate 80% higher risk of developing dementia than people without stroke, according to a study published in the December 4, 2024, online issue of Neurology®, the medical journal of the American Academy of Neurology. The study, which followed older people for an average of 6 years, found 19% of people with stroke and 13% of people without stroke developed dementia. These results do not prove that stroke causes dementia, they only show an association.

The study looked at people with ischemic stroke and intracerebral hemorrhage. Ischemic stroke is caused by a blockage of blood flow to the brain and is the most common type of stroke. Intracerebral hemorrhage is caused by bleeding in the brain.

“As the rates of dementia are rising globally, and more people are surviving stroke, understanding the how stroke contributes to dementia risk is of great importance,” said study author Raed A Joundi MD DPhil, of McMaster University in Hamilton, Canada. “We found that almost one-fifth of stroke survivors are diagnosed with dementia over an average of 6 years and up to 20 years after stroke.”

For the study, researchers looked at health data on people living in Ontario during a 20-year period. They identified 174,817 people with stroke who were matched to the same number of people without stroke for factors such as age, sex, high blood pressure and diabetes. Participants had an average age of 69.

Researchers determined there were 3.3 dementia cases per 100 person-years for people with stroke and 1.9 dementia cases per 100 person-years for matched people without stroke. Person-years represent both the number of people in the study and the amount of time each person spends in the study.

After matching for factors such as age, sex, high blood pressure and diabetes, researchers found people with stroke had a 76% increased risk of dementia when compared to people without stroke.

They also found that risk changed over time, with 2.5 times the risk of dementia 1 year after stroke, a 50% increased risk at 5 years, and 30% increased risk after 20 years.

“Importantly, our research also found that the risk of dementia after stroke was double the risk of having a second stroke,” said Joundi. “While much research has been focused on reducing the risk of a second stroke, our findings make it clear that that more research also is needed on developing interventions to help prevent dementia after stroke.”

A limitation of the study was that although people with a prior diagnosis of dementia were not included, researchers did not have information on cognitive decline in people before having a stroke.

The study was funded by Brain Canada, the Heart & Stroke Foundation of Canada and Canadian Stroke Consortium.

Source: News Release
American Academy of Neurology
December 4, 2024